Systems and methods for treating cardiac arrhythmias

ABSTRACT

An implantable medical device (IMD) may include a housing having a proximal end and a distal end and a set of one or more electrodes connected to but spaced apart from the housing. The IMD may further include a controller disposed within the housing, wherein the controller is configured to sense cardiac electrical signals, and deliver electrical stimulation pulses via the first set of one or more electrodes. In some embodiments, a first portion of the housing is configured to be disposed at least partly within a coronary sinus of a patient&#39;s heart and a second portion of the housing is configured to be disposed at least partly within a right atrium of the patient&#39;s heart.

This is a continuation of co-pending U.S. patent application Ser. No.15/006,928, filed Jan. 26, 2016, which claims the benefit of U.S.Provisional Patent Application Ser. No. 62/113,147 filed on Feb. 6,2015, both of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure generally relates to systems, devices, andmethods for treating cardiac arrhythmias, and more particularly, tosystems, devices, and methods for detecting cardiac arrhythmias anddelivering electrical stimulation therapy to a right atrium, left atriumand/or left ventricle of a heart.

BACKGROUND

Pacing instruments can be used to treat patients suffering from variousheart conditions that result in a reduced ability of the heart todeliver sufficient amounts of blood to a patient's body. These heartconditions may lead to rapid, irregular, and/or inefficient heartcontractions. To help alleviate some of these conditions, variousdevices (e.g., pacemakers, defibrillators, etc.) have been implanted ina patient's body. Such devices may monitor and provide electricalstimulation to the heart to help the heart operate in a more normal,efficient and/or safe manner.

SUMMARY

The present disclosure generally relates to systems, devices, andmethods for treating cardiac arrhythmias, and more particularly, tosystems, devices, and methods for detecting cardiac arrhythmias anddelivering electrical stimulation therapy to a right atrium and/or aleft ventricle of a heart.

In one embodiment, an implantable medical device (IMD) comprises ahousing having a proximal end and a distal end and a first set of one ormore electrodes connected to but spaced apart from the housing. In someembodiments, the IMD may also comprise a controller disposed within thehousing. The controller may be configured to sense cardiac electricalsignals, and deliver electrical stimulation pulses via the first set ofone or more electrodes. In some embodiments, a first portion of thehousing may be configured to be disposed at least partly within acoronary sinus of a patient's heart and a second portion of the housingis configured to be disposed at least partly within a right atrium ofthe patient's heart.

Alternatively, or additionally, in the embodiment above, the housingfurther comprises a fixation element disposed on the portion of thehousing that is configured to be disposed within the coronary sinus.

Alternatively, or additionally, in any of the above embodiments, thehousing further comprises an eccentric bias element disposed on theportion of the housing that is configured to be disposed within thecoronary sinus.

Alternatively, or additionally, in any of the above embodiments, thehousing further comprises a docking hub disposed proximate the proximalend of the housing.

Alternatively, or additionally, in any of the above embodiments, thedocking hub is configured to extend into the right atrium of thepatient's heart.

Alternatively, or additionally, in any of the above embodiments, thehousing comprises at least a first discrete section and a seconddiscrete section, and wherein the first discrete section is configuredto be disposed at least partially within the coronary sinus and thesecond discrete section is configured to be disposed within the rightatrium of the patient's heart.

Alternatively, or additionally, in any of the above embodiments, thefirst discrete section and the second discrete section are connected bya flexible connector section.

Alternatively, or additionally, in any of the above embodiments, thefirst discrete section comprises an energy storage device.

Alternatively, or additionally, in any of the above embodiments, thesecond discrete section comprises a processing module.

Alternatively, or additionally, in any of the above embodiments, atleast a portion of the housing has a non-circular cross-section.

Alternatively, or additionally, in any of the above embodiments, thehousing further comprises a guide-wire entrance port disposed on thefirst portion of the housing.

Alternatively, or additionally, in any of the above embodiments, thefirst set of one or more electrodes is configured to be disposed withinthe right atrium of the patient's heart.

Alternatively, or additionally, in any of the above embodiments, thefirst set of one or more electrodes are disposed on a first extensionextending from the housing.

Alternatively, or additionally, in any of the above embodiments, thefirst extension has a proximal end and a distal end, and wherein theproximal end of the first extension is connected to the housing, andwherein a fixation element is positioned adjacent the distal end.

Alternatively, or additionally, in any of the above embodiments, thefixation element comprises one or more of tines, helical coils, andtalons.

Alternatively, or additionally, in any of the above embodiments, adocking hub is positioned adjacent the distal end of the firstextension.

Alternatively, or additionally, in any of the above embodiments,comprising a second set of one or more electrodes spaced apart from thehousing.

Alternatively, or additionally, in any of the above embodiments, thesecond set of one or more electrodes are configured to be disposedwithin the coronary sinus.

Alternatively, or additionally, in any of the above embodiments, thesecond set of one or more electrodes are disposed on a second extension.

Alternatively, or additionally, in any of the above embodiments, thesecond extension has a proximal end and a distal end, and wherein theproximal end of the second extension is connected to the housing.

Alternatively, or additionally, in any of the above embodiments, thesecond extension further comprises one or more fixation elements, andwherein the one or more fixation elements comprise one or more of tines,helical coils, and metal talons.

Alternatively, or additionally, in any of the above embodiments, atleast part of the second extension is coiled.

Alternatively, or additionally, in any of the above embodiments, thesecond extension further comprises a guide-wire exit port.

In another embodiment, an implantable medical device (IMD) comprises ahousing having a proximal end and a distal end and a first set of one ormore electrodes connected to but spaced apart from the housing. The IMDmay further comprise a controller disposed within the housing, and thecontroller is configured to communicate with one or more medical devicesspaced from the IMD, sense cardiac electrical signals, and deliverelectrical stimulation pulses via the first set of one or moreelectrodes. In some embodiments, the housing is configured to bedisposed at least partly within a coronary sinus of a patient's heart.

Alternatively, or additionally, in the above embodiment, the housingfurther includes a first portion and a second portion, and wherein thefirst a portion of the housing is configured to be disposed at leastpartly within the coronary sinus of the patient's heart and a secondportion of the housing is configured to be disposed at least partlywithin a right atrium of the patient's heart.

Alternatively, or additionally, in any of the above embodiments, thefirst set of electrodes is configured to be disposed within the rightatrium of the patient's heart, and the controller is configured todeliver electrical stimulation to the right atrium of the patient'sheart via the first set of electrodes.

Alternatively, or additionally, in any of the above embodiments, the IMDfurther comprises a second set of one or more electrodes, and whereinthe second set of one or more electrodes are configured to be disposedwithin the coronary sinus.

Alternatively, or additionally, in any of the above embodiments, thecontroller is configured to deliver electrical stimulation to a leftventricle of the patient's heart via the second set of one or moreelectrodes.

Alternatively, or additionally, in any of the above embodiments, the oneor more medical devices comprise one or more of: an implantablecardioverter-defibrillator (ICD);

a subcutaneous implantable cardioverter-defibrillator (SICD); animplantable cardiac pacemaker (ICD); an implantable leadless cardiacpacemaker (LCP); and a device programmer.

Alternatively, or additionally, in any of the above embodiments, thehousing further comprises a docking hub disposed proximate the proximalend of the housing.

Alternatively, or additionally, in any of the above embodiments, thedocking hub is configured to extend into the right atrium of thepatient's heart.

Alternatively, or additionally, in any of the above embodiments, thehousing comprises at least a first discrete section and a seconddiscrete section, and wherein the first discrete section is configuredto be disposed at least partially within the coronary sinus and thesecond discrete section is configured to be disposed within the rightatrium of the patient's heart.

Alternatively, or additionally, in any of the above embodiments, thefirst discrete section and the second discrete section are connected bya flexible connector section.

Alternatively, or additionally, in any of the above embodiments, thefirst discrete section comprises an energy storage device.

Alternatively, or additionally, in any of the above embodiments, thesecond discrete section comprises a processing module.

In yet another embodiment, an implantable medical device (IMD) comprisesa housing having a rigid first portion and a rigid second portion,wherein the rigid first portion and the rigid second portion arephysically connected by a flexible connector. The IMD may additionallycomprise a controller disposed within the housing, and the controller isconfigured to communicate with one or more medical devices spaced fromthe IMD, sense cardiac electrical signals, and deliver electricalstimulation pulses via a first set of one or more electrodes. In someembodiments, the rigid first portion of the housing is configured to bedisposed at least partly within the right atrium of the patient's heart,and the rigid second portion of the housing is configured to be disposedat least partly within a coronary sinus of the patient's heart.Additionally, at least some embodiments may further comprise a fixationelement for holding the rigid second portion of the housing at leastpartly within the coronary sinus of the patient's heart.

Alternatively, or additionally, in the above embodiment, the housingcomprises a docking hub disposed on the rigid first portion.

Alternatively, or additionally, in any of the above embodiments, thefirst set of one or more electrodes are provided on an atrial extensionextending from the rigid first portion, wherein the atrial extensionincludes a fixation element configured to fix the atrial extension tothe an atrium wall of the atrium of the patient's heart.

Alternatively, or additionally, in any of the above embodiments, thefixation element comprises one or more of tines, a helical coil, ormetal talons.

Alternatively, or additionally, in any of the above embodiments, furthercomprising a second set of one or more electrodes, wherein the secondset of one or more electrodes are provided on a ventricle extensionextending from the rigid second portion further into the coronary sinusof the patient's heart, wherein the ventricle extension includes afixation element configured to fix the ventricle extension to a wall ofthe coronary sinus of the patient's heart.

Alternatively, or additionally, in any of the above embodiments, thecontroller is further configured to deliver electrical stimulationpulses via the second set of one or more electrodes.

In another embodiment, an implantable medical device (IMD), comprises anelongated housing and a first head spaced from the elongated housing butconnected to the elongated housing via a first flexible connector, thefirst head comprising a first fixation element for fixing the first headto the heart of the patient. In some embodiments, the first head and/orthe first flexible connector comprising one or more first electrodes.The IMD may further comprise a controller disposed within the elongatedhousing, wherein the controller is configured to deliver electricalstimulation pulses to the heart of the patient via one or more of thefirst electrodes of the first head.

Alternatively, or additionally, in the above embodiment, the elongatedhousing has a length and a maximum width, with a non-circularcross-section across the maximum width to facilitate blood flow past theelongated housing when the elongated housing is disposed at least partlywithin a coronary sinus of a heart of a patient.

Alternatively, or additionally, in any of the above embodiments, theelongated housing comprises a first docking hub.

Alternatively, or additionally, in any of the above embodiments, thefirst head comprises a second docking hub.

Alternatively, or additionally, in any of the above embodiments, thefirst fixation element is configured to pierce through at least part ofthe heart of the patient.

Alternatively, or additionally, in any of the above embodiments, furthercomprising a second head spaced from the elongated housing but connectedto the elongated housing via a second flexible connector, the secondhead comprising a second fixation element for fixing the second head tothe heart of the patient.

Alternatively, or additionally, in any of the above embodiments, thesecond fixation element comprises one or more of tines, helical coils,and talons.

Alternatively, or additionally, in any of the above embodiments, thesecond head and/or the second flexible connector comprising one or moresecond electrodes.

Alternatively, or additionally, in any of the above embodiments, thecontroller is further configured to deliver electrical stimulationpulses to the heart of the patient via one or more of the secondelectrodes of the second head.

Alternatively, or additionally, in any of the above embodiments, thehousing comprises one or more housing electrodes.

Alternatively, or additionally, in any of the above embodiments, thecontroller is further configured to communicate with one or more medicaldevices spaced from the IMD.

Alternatively, or additionally, in any of the above embodiments, thecontroller is configured to communicate with one or more medical devicesspaced from the IMD using one or more housing electrodes that are fixedrelative to the elongated housing.

The above summary is not intended to describe each embodiment or everyimplementation of the present disclosure. Advantages and attainments,together with a more complete understanding of the disclosure, willbecome apparent and appreciated by referring to the followingdescription and claims taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may be more completely understood in consideration of thefollowing description of various illustrative embodiments in connectionwith the accompanying drawings, in which:

FIG. 1 is a schematic diagram of an illustrative medical device system;

FIG. 2 is a schematic block diagram of an illustrative leadless cardiacpacemaker;

FIG. 3 is a schematic block diagram of an illustrative implantablecardioverter-defibrillator;

FIG. 4 is a schematic diagram of an illustrative system that includes anLCP and another medical device;

FIG. 5 is a schematic diagram of an illustrative pacing device;

FIG. 6 is a schematic block diagram of the body of the illustrativepacing device of FIG. 5;

FIG. 7 is another schematic block diagram of a body of anotherillustrative pacing device;

FIG. 8 is a schematic diagram of a distal portion of an illustrativepacing device;

FIGS. 9A-9D are schematic diagrams of illustrative distal ends of anextension of a pacing device;

FIGS. 10A-10B are plan views of illustrative fixation elements for anextension of a pacing device;

FIG. 11 is an illustrative diagram of a pacing device implanted within apatient's heart;

FIG. 12 is an illustrative diagram of another pacing device implantedwithin a patient's heart;

FIGS. 13A-13C are exemplary cross-sections of a pacing device;

FIGS. 14A-14B are illustrative diagrams showing an illustrative pacingdevice being pushed along a guide wire and out the distal end of a guidecatheter;

FIG. 15 is an illustrative diagram of an illustrative pacing devicebeing delivered within a guide catheter;

FIGS. 16A-16B are diagrams of an illustrative interlocking mechanism forengaging and/or disengaging a docking hub of a pacing device;

FIGS. 17A-17C are illustrative diagrams of another illustrativeinterlocking mechanism for engaging and/or disengaging a docking hub ofa pacing device;

FIGS. 18A-18D are illustrative diagrams of an illustrative interlockingmechanism for engaging and/or disengaging a portion of a pacing device;and

FIGS. 19-24 are a series of diagrams that show delivery of anillustrative pacing device into a patient's heart.

While the disclosure is amenable to various modifications andalternative forms, specifics thereof have been shown by way ofembodiment in the drawings and will be described in detail. It should beunderstood, however, that the intention is not to limit aspects of thedisclosure to the particular illustrative embodiments described. On thecontrary, the intention is to cover all modifications, equivalents, andalternatives falling within the spirit and scope of the disclosure.

DESCRIPTION

The following description should be read with reference to the drawingsin which similar elements in different drawings are numbered the same.The description and the drawings, which are not necessarily to scale,depict illustrative embodiments and are not intended to limit the scopeof the disclosure.

This disclosure describes systems, devices, and methods for detectingand treating cardiac arrhythmias, and more particularly, to systems,devices, and methods for delivering electrical stimulation therapy to aright atrium, left atrium and/or a left ventricle of a heart of apatient. For instance, one or more devices may be implanted on or withina patient's heart, and the one or more devices may be configured todeliver electrical stimulation therapy to one or more chambers of thepatient's heart in accordance with one or more therapy programs and/orto treat one or more types of detected cardiac arrhythmias. Some exampleelectrical stimulation therapies include bradycardia therapy, cardiacresynchronization therapy (CRT), anti-tachycardia pacing (ATP) therapy,defibrillation and/or cardioversion therapy, and the like. Some examplecardiac arrhythmias include atrial fibrillation or atrial flutter,ventricular fibrillation, and tachycardia.

FIG. 1 is a conceptual diagram of an illustrative system for deliveringelectrical stimulation therapy to a patient's heart, includingdelivering electrical stimulation therapy to a right atrium, leftatrium, and/or a left ventricle of the patient's heart. FIG. 1 shows anillustrative system 20 implanted in and around heart 10. Heart 10 ofFIG. 1 is depicted showing right atrium 21, left atrium 23, rightventricle 25, left ventricle 27, coronary sinus 11, coronary sinusostium 12, great cardiac vein 13, and septum 15.

FIG. 1 depicts system 20 as including a pacing device 500, a leadlesscardiac pacemaker (LCP) 550, and an implantablecardioverter-defibrillator (ICD) 600. In the embodiment of FIG. 1,illustrative pacing device 500 includes housing or body 502 having aproximal end and a distal end and extensions 501, 503. However, in someinstances, extension 501 and/or extension 503 may not be included. Insome embodiments, body 502 may include two body portions 502 a, 502 bconnected by connection 511, with body portion 502 a disposed at thedistal end of body 502 and body portion 502 b disposed the proximal endof body 502. In some cases, connection 511 may be a flexible connectionwhich may allow body portions 502 a and 502 b to move relative to oneanother. Additionally, when implanted, body portion 502 a may be fullyor partially disposed within coronary sinus 11 of the patient's heart,while body portion 502 b may be disposed fully or partially within rightatrium 21.

In some embodiments, pacing device 500 may additionally include one ormore electrodes 507 a-507 d. Although electrodes 507 a-507 d aredepicted as disposed on both body portions 502 a, 502 b, in some cases,the number and location of electrodes disposed on body 502 may vary,depending on the application. For example, pacing device 500 may onlyhave electrodes disposed on one body portion 502 a or 502 b where pacingdevice 500 includes two body portions. In some instances, pacing device500 may not have any electrodes disposed on body 502. When provided,electrodes 507 a-507 d may be used to deliver electrical stimulation toheart 10, and/or sense one or more physiologic signals. In some cases,pacing device 500 may use one or more of the electrodes 507 a-507 d tocommunicate with one or more other devices, such as LCP 550 and/or ICD600. In some instances, pacing device 500 may communicate usingconducted communication techniques, as will be described with respect toother figures, and may deliver and/or receive communication signalsthrough one or more of the electrodes 507 a-507 d.

In some instances, body 502 may include a docking hub 504 which extendsgenerally from the proximal end of body 502. In the example shown inFIG. 1, docking hub 504 may extend from body portion 502 a. Duringimplantation, docking hub 504 may be releasably coupled to a positioningdevice (not shown). When coupled, movement of the positioning device maytranslate to body 502, thereby allowing a user, such as a physician, tomaneuver body 502 into a proper position within heart 10, for exampleinto or proximate coronary sinus 11.

In some instances, docking hub 504 may be a retrieval hub. Accordingly,during implantation, docking hub may not releasably couple to apositioning device. Rather, pacing device 500 may be delivered from aguide catheter, and the portion of the guide catheter surrounding body502 may conform to body 502 to create a secure connection between theguide catheter and body 502. When in position, the guide catheter may beretracted, or a stylet or other pushing device may push body 502 out ofthe guide catheter. In these cases, docking hub 504 may further includea tether anchor. During delivery, a tether may be coupled to the tetheranchor to allow a user to pull body 502 back within the guide catheterfor further positioning. In some instances, the tether is a string, andthe string may be coupled to the tether anchor by looping around thetether anchor. To release the tether from body 502, a user may simplycut the tether or pull one end of the tether until the tether unloopsitself from the tether anchor.

In some cases, body 502 may include extension 503 extending from theproximal end of body 502, or body portion 502 b as shown in FIG. 1. Whenimplanted, extension 503 may extend from body 502 to near septum 15 ofheart 10. The distal end of extension 503 may include one or morefixation elements 506. Fixation elements 506 may secure the distal endof extension 503 in right atrium 21 proximate septum 15, or, in someinstances, directly to septum 15. In some embodiments, fixation elements506 may include one or more tines made of silicon, a biocompatiblepolymer, a biocompatible metal, or another biocompatible material. Insuch embodiments, the tines may be embedded within trabeculae of rightatrium 21 proximate septum 15 to help provide a stable connection. Inother embodiments, fixation elements 506 may comprise one or more of ahelical coil or talons.

In some cases, extension 503 may include one or more electrodes 505a-505 e. When provided, electrodes 505 a-505 e may be disposed proximatethe distal end of extension 503, however in other embodiments,electrodes 505 a-505 e may span the length of extension 503. In thismanner, in some embodiments, electrodes 505 a-505 e may be spaced apartfrom body 502. In some instances, some or all of electrodes 505 a-505 emay be used to deliver electrical stimulation to heart 10, and moreparticularly, to the right atrium of the heart. For instance, in theexample shown in FIG. 1, pacing device 500 may deliver electricalstimulation to right atrium 21 of heart 10 through a set of one or moreof the electrodes 505 a-505 e. As used herein, the set of electrodes bywhich pacing device 500 may deliver electrical stimulation may be termedthe second set, and the set of electrodes by which pacing device 500 maydeliver communication signals may be termed the first set. The secondset of electrodes may include any pair of electrodes 505 a-505 e.Although, in other embodiments, the second set of electrodes may includemore than two electrodes, and in general may include any combination ofelectrodes 505 a-505 e. In general, examples of electrical stimulationmay include pacing pulses delivered in accordance with one or moreprogrammed electrical stimulation therapies. In some cases, pacingdevice 500 may use one or more of the electrodes 505 a-505 e tocommunicate with one or more other devices. For instance, pacing device500 may communicate using conducted communication techniques, as will bedescribed with respect to other figures, and may deliver and/or receivecommunication signals through one or more of the electrodes 505 a-505 e.

In some cases, extension 503 may include a docking hub 508, which mayextend from the proximal end of extension 503. During implantation,docking hub 508 may be releasably coupled to a positioning device (notshown). When coupled, movement of the positioning device may translateto the proximal end of extension 503, thereby allowing a user, such asphysician, to maneuver the proximal end extension 503 into positionwithin heart 10, for example proximate septum 15.

Although extension 501 is depicted in FIG. 1, in some embodiments,pacing device 500 may not include extension 501 and/or extension 503.Where pacing device 500 includes both extensions 501 and 503, extension501 may extend from the distal end of body 502, for example body portion502 a, as shown in FIG. 1. When included, extension 501 may extend intocoronary sinus 12 and be secured within coronary sinus 12. In somecases, extension 501 may extend through coronary sinus 12 and into greatcardiac vein 13, as depicted in FIG. 1. The distal end of extension 501may include one or more fixation elements 512. Fixation elements 512 mayhelp secure the distal end of extension 501 within coronary sinus 12 orgreat cardiac vein 13. Fixation elements 512 may include one or moretines made of silicon, a biocompatible polymer, a biocompatible metal,or another biocompatible material. In such embodiments, the tines mayextend outward from extension 501 and press against the walls of greatcardiac vein 13. The friction between the tines and the walls of greatcardiac vein 13 may hold the distal end of extension 501 in place. Inother embodiments, fixation elements 512 may comprise one or more of ahelical coil and talons.

Extension 501 may include one or more electrodes 510 a-510 e. In some ofthese embodiments, electrodes 510 a-510 e may be disposed proximate thedistal end of extension 501 and away from body 502, however in otherembodiments, electrodes 510 a-510 e may span the length of extension501. Accordingly, in this manner, electrodes 510 a-510 e may be spacedapart from body 502. In some cases, electrodes 510 a-510 e may be usedto deliver electrical stimulation to heart 10. For example, pacingdevice 500 may deliver electrical stimulation to the left ventricle 27of heart 10 through a set of one or more of electrodes 510 a-510 e.Where pacing device 500 does deliver electrical stimulation to leftventricle 27, the second set of electrodes mentioned above mayadditionally include any of electrodes 510 a-510 e. Although, pacingdevice 500 may use different electrode combinations from the second setof electrodes to deliver electrical stimulation to right atrium 21, leftatrium 23, and/or left ventricle 27. Additionally, or alternatively, insome cases, pacing device 500 may deliver electrical stimulation to theleft ventricle 27 of heart 10 using two or more of electrodes 510 a-510e, either simultaneously or with a delay (e.g. via multi-electrodepacing).

In still some additional or alternative cases, pacing device 500 may useone or more of the electrodes 510 a-510 e to communicate with one ormore other devices. For instance, pacing device 500 may communicateusing conducted communication techniques, as will be described withrespect to other figures, and may deliver and/or receive communicationsignals through one or more of the electrodes 510 a-510 e.

In some cases, system 20 may include only pacing device 500 implanted asa single device (e.g. without LCP 550 or ICD 600), which may provideelectrical stimulation to the right atrium 21, left atrium 23, and/orleft ventricle 27, as desired. For instance, pacing device 500 may beconfigured to deliver electrical stimulation in accordance with atherapy program to treat atrial fibrillation or atrial flutter. However,in other cases, such as depicted in FIG. 1, system 20 may additionallyinclude an LCP 550, such as the an LCP 550 in the right ventricle.Although LCP 550 is depicted implanted in right ventricle 25, in somecases, an LCP 550 may be implanted in other chambers of heart 10, suchas left atrium 23, or left ventricle 27, or at various locations on theoutside of heart 10. In some cases, system 20 may include multiple LCPdevices implanted at various locations.

Where system 20 includes LCP 550 implanted within right ventricle 25 inaddition to pacing device 500, LCP 550 and pacing device 500 may beconfigured to deliver electrical stimulation therapy to heart 10. Forinstance, LCP 550 may be configured to deliver electrical stimulationtherapy to right ventricle 25 by delivering pacing pulses to the rightventricle 25 in a pattern according to a therapy program, sometimesincluding rate-responsive pacing, and/or delivering anti-tachycardiapacing (ATP) therapy. In embodiments including both pacing device 500and LCP 550, system 20 may be configured to deliver electricalstimulation therapies such as ATP, CRT, and/or other electricalstimulation therapies to treat cardiac abnormalities such asbradycardia, tachycardia, ventricular desynchronization, atrialfibrillation or atrial flutter, and ventricular fibrillation.

In some embodiments, pacing device 500 may be part of a single ormultiple device system for delivering cardiac resynchronization therapy(CRT) to heart 10. In some of these embodiments, pacing device 500 maysense cardiac electrical signals in one or more of right atrium 21 andleft atrium 23. Once pacing device 500 senses cardiac electrical signalspropagating through right atrium 21 and/or left atrium 23, pacing device500 may deliver a pacing pulse to left ventricle 27 after a delay period(e.g. an AV delay). The length of the delay period may be determined orchosen such that pacing device 500 may deliver a pacing pulse to leftventricle 27 as the propagating cardiac electrical signals reach rightventricle 25 and cause right ventricle 25 to contract. In this manner,pacing device 500 may operate to provide synchronous contractions ofright ventricle 25 and left ventricle 27. In some additionalembodiments, pacing device 500 may adjust the delay period based on asensed heart rate. For instance, when pacing device 500 senses anincreased heart rate, pacing device 500 may shorten the length of thedelay period. Conversely, when pacing device 500 senses a lowered heartrate, pacing device 500 may lengthen the delay period.

In other embodiments, pacing device 500 may deliver pacing pulses toright atrium 21 and/or left atrium 23. In these embodiments, pacingdevice may begin counting the delay period at the time of or just afterpacing device 500 delivers a pacing pulse to right atrium 21 and/or leftatrium 23. As with the previously described embodiments, this may causesynchronous contractions of right ventricle 25 and left ventricle 27.Where pacing device 500 is part of a system with an LCP implanted withinright ventricle 25, pacing device 500 may communicate a trigger to theLCP after pacing device 500 delivers a pacing pulse to right atrium 21and/or left atrium 23. After receiving the trigger, the LCP may delivera pacing pulse to right ventricle 25 after its own delay period. In atleast some of the examples, the delay period of the LCP and the delayperiod of pacing device 500 may be in alignment such that both the LCPand pacing device 500 deliver pacing pulses to right ventricle 25 andleft ventricle 27 synchronously. However, in other embodiments, thedelay period of the LCP and the delay period of pacing device 500 may bedifferent, for instance if conduction through right ventricle 25 andleft ventricle 27 differ, in order to cause right ventricle 25 and leftventricle 27 to contract synchronously.

As depicted in FIG. 1, LCP 550 may include one or more fixation members553. In the example shown, the one or more fixation members 553 maysecure LCP 550 within right ventricle 25. Additionally, LCP 550 mayinclude electrodes 552 a, 552 b. In some cases, LCP 550 may includeanother electrode (not shown) near the fixation members 553 to engagethe heart tissue. Where LCP 550 is configured to deliver electricalstimulation therapy, LCP 550 may deliver electrical stimulation therapyvia electrodes 552 a, 552 b and/or another electrode. Additionally, LCP550 may be configured to communicate with one or more other devices. Insuch embodiments, and where LCP 550 is configured to communicate usingconducted communication, LCP 550 may be configured to deliver and/orreceive communication signals via one or more of the electrodes 552 a,552 b.

In some instances, system 20 may include an implantablecardioverter-defibrillator (ICD) 600. ICD 600 may include housing 601,lead 603, and electrodes 602 a-602 c, which in some embodiments may bespaced apart from housing 601. For example, electrodes 602 a-602 c maybe located on one or more leads attached to housing 601. In someembodiments, ICD 600 is a subcutaneous ICD (SICD), and lead 603 may be asubcutaneously implanted lead as shown in FIG. 1. In some cases, ICD 600may be configured to deliver electrical stimulation to heart 10. Forinstance, ICD 600 may be configured to deliver cardioversion and/ordefibrillation therapy to heart 10. In such embodiments, ICD 600 maydeliver such electrical stimulation therapy via one or more electrodes602-602 c. In some cases, ICD 600 may be configured to communicate withone or more other devices. Where ICD 600 is configured to communicatevia conducted communication, ICD 600 may be configured to send and/orreceive communication signals via one or more of the electrodes 602a-602 c.

FIG. 2 is a conceptual schematic of an exemplary LCP 550 that may beused in system 20. Generally, LCP 550 may operate to sense physiologicalsignals and parameters and deliver one or more types of electricalstimulation therapy to tissues of the patient. As can be seen in FIG. 2,LCP 550 may be a compact device with all components housed within LCP550 or directly on housing 720. LCP 550 may include communication module702, pulse generator module 704, electrical sensing module 706,mechanical sensing module 708, processing module 710, energy storagemodule 712, and electrodes 714.

As depicted in FIG. 2, LCP 550 may include electrodes 714, which can besecured relative to housing 720 and electrically exposed to tissueand/or blood surrounding LCP 550. Electrodes 714 may generally conductelectrical signals to and from LCP 550 and the surrounding tissue and/orblood. Such electrical signals can include electrical communicationsignals, electrical stimulation pulses, and intrinsic cardiac electricalsignals, to name a few. Intrinsic cardiac electrical signals may includeelectrical signals generated by the heart and may be represented by anelectrocardiogram (ECG).

Electrodes 714 may include one or more biocompatible conductivematerials such as various metals or alloys that are known to be safe forimplantation within a human body. In some instances, electrodes 714 maybe generally disposed on either end of LCP 550 and may be in electricalcommunication with one or more of modules 702, 704, 706, 708, and 710.In embodiments where electrodes 714 are secured directly to housing 720,an insulative material may electrically isolate the electrodes 714 fromadjacent electrodes, housing 720, and/or other parts of LCP 550. In someinstances, some or all of electrodes 714 may be spaced from housing 720and connected to housing 720 and/or other components of LCP 550 throughconnecting wires. In such instances, the electrodes 714 may be placed ona tail (not shown) that extends out away from the housing 720. As shownin FIG. 2, in some embodiments, LCP 550 may include electrodes 714′.Electrodes 714′ may be in addition to electrodes 714, or may replace oneor more of electrodes 714. Electrodes 714′ may be similar to electrodes714 except that electrodes 714′ are disposed on the sides of LCP 550. Insome cases, electrodes 714′ may increase the number of electrodes bywhich LCP 550 may deliver electrical communication signals and/orelectrical stimulation pulses, and/or may sense intrinsic cardiacelectrical signals, electrical communication signals, and/or electricalstimulation pulses.

Electrodes 714 and/or 714′ may assume any of a variety of sizes and/orshapes, and may be spaced at any of a variety of spacings. For example,electrodes 714 may have an outer diameter of two to twenty millimeters(mm). In other embodiments, electrodes 714 and/or 714′ may have adiameter of two, three, five, seven millimeters (mm), or any othersuitable diameter, dimension and/or shape. Example lengths forelectrodes 714 and/or 714′ may include, for example, one, three, five,ten millimeters (mm), or any other suitable length. As used herein, thelength is a dimension of electrodes 714 and/or 714′ that extends awayfrom the outer surface of the housing 720. In some instances, at leastsome of electrodes 714 and/or 714′ may be spaced from one another by adistance of twenty, thirty, forty, fifty millimeters (mm), or any othersuitable spacing. The electrodes 714 and/or 714′ of a single device mayhave different sizes with respect to each other, and the spacing and/orlengths of the electrodes on the device may or may not be uniform.

In the embodiment shown, communication module 702 may be electricallycoupled to electrodes 714 and/or 714′ and may be configured to delivercommunication signals, such as electrical communication pulses, totissues of the patient for communicating with other devices such assensors, programmers, other medical devices, and/or the like. Electricalcommunication pulses, as used herein, may be any modulated signal thatconveys information to another device, either by itself or inconjunction with one or more other modulated signals. In someembodiments, electrical communication pulses may be limited tosub-threshold signals that do not result in capture of the heart yetstill convey information. The electrical communication pulses may bedelivered to another device that is located either external or internalto the patient's body. Communication module 702 may additionally beconfigured to sense for electrical communication pulses delivered byother devices, which may be located external or internal to thepatient's body.

Communication module 702 may communicate to help accomplish one or moredesired functions. Some example functions include delivering senseddata, using communicated data for determining occurrences of events suchas arrhythmias, coordinating delivery of electrical stimulation therapy,and/or other functions. In some cases, LCP 550 may use electricalcommunication pulses to communicate raw information, processedinformation, messages and/or commands, and/or other data. Rawinformation may include information such as sensed electrical signals(e.g. a sensed ECG), signals gathered from coupled sensors, and thelike. In some embodiments, the processed information may include signalsthat have been filtered using one or more signal processing techniques.Processed information may also include parameters and/or events that aredetermined by the LCP 550 and/or another device, such as a determinedheart rate, timing of determined heartbeats, timing of other determinedevents, determinations of threshold crossings, expirations of monitoredtime periods, activity level parameters, blood-oxygen parameters, bloodpressure parameters, heart sound parameters, and the like. Messagesand/or commands may include instructions or the like directing anotherdevice to take action, notifications of imminent actions of the sendingdevice, requests for reading from the receiving device, requests forwriting data to the receiving device, information messages, and/or othermessages commands.

In at least some embodiments, communication module 702 (or LCP 550) mayfurther include switching circuitry to selectively connect one or moreof electrodes 714 and/or 714′ to communication module 702 in order toselect which electrodes 714 and/or 714′ that communication module 702delivers electrical communication pulses. It is contemplated thatcommunication module 702 may communicate with other devices viaconducted signals, radio frequency (RF) signals, optical signals,acoustic signals, inductive coupling, and/or any other suitablecommunication methodology.

In the embodiment shown, a pulse generator module 704 may beelectrically connected to one or more of electrodes 714 and/or 714′.Pulse generator module 704 may be configured to generate electricalstimulation pulses and deliver the electrical stimulation pulses totissues of a patient via one or more of the electrodes 714 and/or 714′in order to effectuate one or more electrical stimulation therapies.Electrical stimulation pulses as used herein are meant to encompass anyelectrical signals that may be delivered to tissue of a patient forpurposes of treatment of any type of disease or abnormality. Forexample, when used to treat heart disease, the pulse generator module704 may generate electrical stimulation pacing pulses for capturing theheart of the patient, i.e. causing the heart to contract in response tothe delivered electrical stimulation pulse. In another embodiment, theelectrical stimulation pulses may be defibrillation/cardioversion pulsesfor shocking the heart out of fibrillation. In yet another embodiment,the electrical stimulation pulses may be anti-tachycardia pacing (ATP)pulses. These are just some examples. When used to treat other ailments,the pulse generator module 704 may generate electrical stimulationpulses suitable for neurostimulation therapy or the like. Pulsegenerator module 704 may include one or more capacitor elements and/orother charge storage devices to aid in generating and deliveringappropriate electrical stimulation pulses. In the embodiment shown,pulse generator module 704 may use energy stored in energy storagemodule 712 to generate the electrical stimulation pulses.

Pulse generator module 704 may include the capability to modify theelectrical stimulation pulses, such as by adjusting the pulse widthand/or amplitude of the electrical stimulation pulses. When pacing theheart, this may help tailor the electrical stimulation pulses to capturethe heart a particular patient, sometimes with reduced battery usage.For neurostimulation therapy, adjusting the pulse width and/or amplitudemay help tailor the therapy for a particular application and/or helpmake the therapy more effective for a particular patient.

Although depicted as separate modules, in some embodiments, LCP 550 mayinclude a combined communication module 702/pulse generator module 704.For instance, pulse generator module 704 may be configured to alsogenerate electrical communication pulses. In such embodiments, pulsegenerator 704 may be configured to generate and deliver both electricalcommunication pulses and electrical stimulation pulses.

In some embodiments, LCP 550 may include an electrical sensing module706 and mechanical sensing module 708. Electrical sensing module 706 maybe configured to sense intrinsic cardiac electrical signals conductedfrom electrodes 714 and/or 714′ to electrical sensing module 706. Forexample, electrical sensing module 706 may be electrically connected toone or more electrodes 714 and/or 714′ and electrical sensing module 706may be configured to receive cardiac electrical signals conductedthrough electrodes 714 and/or 714′. In some embodiments, the cardiacelectrical signals may represent local information from the chamber inwhich LCP 550 is implanted. For instance, if LCP 550 is implanted withina ventricle of the heart, cardiac electrical signals sensed by LCP 550through electrodes 714 and/or 714′ may represent ventricular cardiacelectrical signals. Mechanical sensing module 708 may include, or beelectrically connected to, various sensors, such as accelerometers,blood pressure sensors, heart sound sensors, blood-oxygen sensors,and/or other sensors which measure one or more physiological parametersof the heart and/or patient. Mechanical sensing module 708, whenpresent, may gather signals from the sensors indicative of the variousphysiological parameters. Both electrical sensing module 706 andmechanical sensing module 708 may be connected to processing module 710and may provide signals representative of the sensed cardiac electricalsignals and/or physiological signals to processing module 710. Althoughdescribed with respect to FIG. 2 as separate sensing modules, in someembodiments, electrical sensing module 706 and mechanical sensing module108 may be combined into a single module.

Processing module 710 may be configured to control the operation of LCP550. For example, processing module 710 may be configured to receivecardiac electrical signals from electrical sensing module 706 and/orphysiological signals from mechanical sensing module 708. Based on thereceived signals, processing module 710 may determine, for example,occurrences and types of arrhythmias. Processing module 710 may furtherreceive information from communication module 702. In some embodiments,processing module 710 may additionally use such received information todetermine occurrences and types of arrhythmias. However, in otherembodiments, LCP 550 may use the received information instead of thesignals received from electrical sensing module 706 and/or mechanicalsensing module 708—for instance if the received information is moreaccurate than the signals received from electrical sensing module 706and/or mechanical sensing module 708 or if electrical sensing module 706and/or mechanical sensing module 708 have been disabled or omitted fromLCP 700.

Based on a determined arrhythmia, processing module 710 may controlpulse generator module 704 to generate electrical stimulation pulses inaccordance with one or more electrical stimulation therapies to treatthe determined arrhythmia. For example, processing module 710 maycontrol pulse generator module 704 to generate pacing pulses withvarying parameters and in different sequences to effectuate one or moreelectrical stimulation therapies. For example, in controlling pulsegenerator module 704 to deliver bradycardia pacing therapy, processingmodule 710 may control pulse generator module 704 to deliver pacingpulses designed to capture the heart of the patient at a regularinterval to help prevent the heart of a patient from falling below apredetermined threshold. In some cases, the rate of pacing may beincreased with an increased activity level of the patient (e.g. rateadaptive pacing). For ATP therapy, processing module 710 may controlpulse generator module 704 to deliver pacing pulses at a rate fasterthan an intrinsic heart rate of a patient in attempt to force the heartto beat in response to the delivered pacing pulses rather than inresponse to intrinsic cardiac electrical signals. Once the heart isfollowing the pacing pulses, processing module 710 may control pulsegenerator module 704 to reduce the rate of delivered pacing pulses downto a safer level. In CRT, processing module 710 may control pulsegenerator module 704 to deliver pacing pulses in coordination withanother device to cause the heart to contract more efficiently. In caseswhere pulse generator module 704 is capable of generating defibrillationand/or cardioversion pulses for defibrillation/cardioversion therapy,processing module 710 may control pulse generator module 704 to generatesuch defibrillation and/or cardioversion pulses. In some cases,processing module 710 may control pulse generator module 704 to generateelectrical stimulation pulses to provide electrical stimulationtherapies different than those examples described above.

Aside from controlling pulse generator module 704 to generate differenttypes of electrical stimulation pulses and in different sequences, insome embodiments, processing module 710 may also control pulse generatormodule 704 to generate the various electrical stimulation pulses withvarying pulse parameters. For example, each electrical stimulation pulsemay have a pulse width and a pulse amplitude. Processing module 710 maycontrol pulse generator module 704 to generate the various electricalstimulation pulses with specific pulse widths and pulse amplitudes. Asone example, processing module 710 may cause pulse generator module 704to adjust the pulse width and/or the pulse amplitude of electricalstimulation pulses if the electrical stimulation pulses are noteffectively capturing the heart. Such control of the specific parametersof the various electrical stimulation pulses may help LCP 550 providemore effective delivery of electrical stimulation therapy.

In some embodiments, processing module 710 may further controlcommunication module 702 to send information to other devices. Forexample, processing module 710 may control communication module 702 togenerate one or more electrical communication pulses for communicatingwith other devices of a system of devices. For instance, processingmodule 710 may control communication module 702 to generate electricalcommunication pulses in particular sequences, where the specificsequences convey different information. Communication module 702 mayalso receive communication signals for potential action by processingmodule 710.

In further embodiments, processing module 710 may control switchingcircuitry by which communication module 702 and pulse generator module704 deliver electrical communication pulses and/or electricalstimulation pulses to tissue of the patient. As described above, bothcommunication module 702 and pulse generator module 704 may includecircuitry for connecting one or more electrodes 714 and/714′ tocommunication module 702 and/or pulse generator module 704 so thosemodules may deliver the electrical communication pulses and electricalstimulation pulses to tissue of the patient. The specific combination ofone or more electrodes by which communication module 702 and/or pulsegenerator module 704 deliver electrical communication pulses andelectrical stimulation pulses may influence the reception ofcommunication pulses and/or the effectiveness of electrical stimulationpulses. Although it was described that each of communication module 702and pulse generator module 704 may include switching circuitry, in someembodiments, LCP 550 may have a single switching module connected to thecommunication module 702, the pulse generator module 704, and electrodes714 and/or 714′. In such embodiments, processing module 710 may controlthe switching module to connect modules 702/704 and electrodes 714/714′as appropriate.

In some embodiments, processing module 710 may include a pre-programmedchip, such as a very-large-scale integration (VLSI) chip or anapplication specific integrated circuit (ASIC). In such embodiments, thechip may be pre-programmed with control logic in order to control theoperation of LCP 550. By using a pre-programmed chip, processing module710 may use less power than other programmable circuits while able tomaintain basic functionality, thereby potentially increasing the batterylife of LCP 550. In other instances, processing module 710 may include aprogrammable microprocessor or the like. Such a programmablemicroprocessor may allow a user to adjust the control logic of LCP 550after manufacture, thereby allowing for greater flexibility of LCP 550than when using a pre-programmed chip.

Processing module 710, in additional embodiments, may include a memorycircuit and processing module 710 may store information on and readinformation from the memory circuit. In other embodiments, LCP 550 mayinclude a separate memory circuit (not shown) that is in communicationwith processing module 710, such that processing module 710 may read andwrite information to and from the separate memory circuit. The memorycircuit, whether part of processing module 710 or separate fromprocessing module 710, may be volatile memory, non-volatile memory, or acombination of volatile memory and non-volatile memory.

Energy storage module 712 may provide a power source to LCP 550 for itsoperations. In some embodiments, energy storage module 712 may be anon-rechargeable lithium-based battery. In other embodiments, thenon-rechargeable battery may be made from other suitable materials. Insome embodiments, energy storage module 712 may include a rechargeablebattery. In still other embodiments, energy storage module 712 mayinclude other types of energy storage devices such as super capacitors.

To implant LCP 550 inside a patient's body, an operator (e.g., aphysician, clinician, etc.), may fix LCP 550 to the cardiac tissue ofthe patient's heart. To facilitate fixation, LCP 550 may include one ormore anchors 716. Anchor 716 may include any number of fixation oranchoring mechanisms. For example, anchor 716 may include one or morepins, staples, threads, screws, helix, tines, and/or the like. In someembodiments, although not shown, anchor 716 may include threads on itsexternal surface that may run along at least a partial length of anchor716. The threads may provide friction between the cardiac tissue and theanchor to help fix anchor 716 within the cardiac tissue. In otherembodiments, anchor 716 may include other structures such as barbs,spikes, or the like to facilitate engagement with the surroundingcardiac tissue.

FIG. 3 depicts an embodiment of ICD 600, which may operate to sensephysiological signals and/or parameters and deliver one or more types ofelectrical stimulation therapy to tissues of the patient. In theembodiment shown, ICD 600 may include a communication module 802, apulse generator module 804, an electrical sensing module 806, amechanical sensing module 808, a processing module 810, and an energystorage module 818. Each of modules 802, 804, 806, 808, and 810 may besimilar to modules 702, 704, 706, 708, and 710 of LCP 550. Additionally,energy storage module 818 may be similar to energy storage module 712 ofLCP 550. In some embodiments, however, ICD 600 may have a larger volumewithin housing 820. In such embodiments, ICD 600 may include a largerenergy storage module 818 and/or a larger processing module 810 capableof handling more complex operations than processing module 710 of LCP550.

As illustrated in FIG. 3, ICD 600 may include one or more leads 812.Leads 812 may include electrical wires that conduct electrical signalsbetween electrodes 814 and one or more modules located within housing820. In some cases, leads 812 may be connected to and extend away fromhousing 820 of ICD 600. In some embodiments, leads 812 may be implantedon, within, or adjacent to a heart of a patient. Leads 812 may containone or more electrodes 814 positioned at various locations on leads 812and various distances from housing 820. Some leads 812 may only includea single electrode 814, while other leads 812 may include multipleelectrodes 814. Generally, electrodes 814 are positioned on leads 812such that when leads 812 are implanted within the patient, one or moreof the electrodes 814 are positioned to perform a desired function. Insome cases, the one or more of the electrodes 814 may be in contact withthe patient's cardiac tissue. In other cases, the one or more of theelectrodes 814 may be positioned subcutaneously but adjacent thepatient's heart, as are electrodes 602 a-602 c depicted in FIG. 1. Theelectrodes 814 may conduct intrinsically generated electrical cardiacsignals to leads 812. Leads 812 may, in turn, conduct the receivedelectrical cardiac signals to one or more of the modules 802, 804, 806,and 808 of ICD 600. In some cases, ICD 600 may generate electricalstimulation signals, and leads 812 may conduct the generated electricalstimulation signals to electrodes 814. Electrodes 814 may then conductthe electrical stimulation signals to the cardiac tissue of the patient(either directly or indirectly). ICD 600 may also include one or moreelectrodes 814 not disposed on a lead 812. For example, one or moreelectrodes 814 may be connected directly to housing 820.

Leads 812, in some embodiments, may additionally contain one or moresensors, such as accelerometers, blood pressure sensors, heart soundsensors, blood-oxygen sensors, and/or other sensors which are configuredto measure one or more physiological parameters of the heart and/orpatient. In such embodiments, mechanical sensing module 808 may be inelectrical communication with leads 812 and may receive signalsgenerated from such sensors.

Where housing 820 is implantable, housing 820 may be implanted in, forexample, a transthoracic region of the patient. Housing 820 maygenerally include any of a number of known materials that are safe forimplantation in a human body and may, when implanted, hermetically sealthe various components of ICD 600 from fluids and tissues of thepatient's body. In such embodiments, leads 812 may be implanted at oneor more various locations within the patient, such as within the heartof the patient, adjacent to the heart of the patient, adjacent to thespine of the patient, or any other desired location.

In some embodiments, ICD 600 may be configured to sense electricalcardiac signals, determine occurrences of tachyarrhythmias based on thesensed electrical cardiac signals, and deliver defibrillation and/orcardioversion therapy in response to determining an occurrence of atachyarrhythmia (for example by delivering defibrillation and/orcardioversion pulses to the heart of the patient). Where ICD 600 is asubcutaneous implantable cardioverter-defibrillator (SICD), although notrequired in all such embodiments, one of leads 812 may be asubcutaneously implanted lead. In at least some of these embodiments ICD600 may include only a single lead which is implanted subcutaneously butoutside of the chest cavity.

FIG. 4 illustrates an example medical device system 900 and acommunication pathway through which multiple medical devices 902, 904,905, 906, and/or 910 of system 900 may communicate. In the exampleshown, medical device system 900 may include pacing device 902, LCP 904,ICD 905, external medical device 906, and other sensors/devices 910.External device 906 may be a device disposed external to a patient'sbody. Other sensors/devices 910 may be, for example, various diagnosticsensors that gather information about the patient, such asaccelerometers, blood pressure sensors, or the like. These sensors canbe internal or external of the patient's body. In some cases, othersensors/devices 910 may include an external programmer device that maybe used to program one or more devices of system 900.

In the example shown in FIG. 4, various devices of system 900 maycommunicate via communication pathway 908. For instance, pacing device902, LCP 904, and/or ICD 905 may sense intrinsic cardiac electricalsignals and may communicate such signals, or events based on suchsignals, to one or more other devices 902, 904, 905, 906, and 910 ofsystem 900 via communication pathway 908. In one embodiment, one or moreof devices 902, 904, and 905 may receive such signals and, based on thereceived signals, determine an occurrence of an arrhythmia or otherphysiological condition. In some cases, device or devices 902, 904,and/or 905 may communicate such determinations to one or more otherdevices 906 and 910 of system 900. In some cases, one or more of devices902, 904, 905, 906, and 910 of system 900 may take action based on thecommunicated determination of an arrhythmia or other physiologicalcondition, such as by delivering a suitable electrical stimulation tothe heart of the patient. One or more of devices 902, 904, 905, 906, and910 of system 900 may additionally communicate command or responsemessages via communication pathway 908. The command messages may cause areceiving device to take a particular action, whereas response messagesmay include requested information or a confirmation that a receivingdevice did, in fact, receive a communicated message or data.

It is contemplated that the various devices of system 900 maycommunicate via pathway 908 using conducted signals, RF signals,inductive coupling, optical signals, acoustic signals, or any othersignals suitable for communication. In some instances, the variousdevices of system 900 may communicate via pathway 908 using differentsignal types. For instance, other sensors/device 910 may communicatewith external device 906 using a first signal type (e.g. RFcommunication) but may communicate with pacing device 902 and/or LCP 904using a second signal type (e.g. conducted communication). Further, insome embodiments, communication between devices may be limited. Forinstance, in some embodiments, pacing device 902 and/or LCP 904 maycommunicate with external device 906 only through other sensors/devices910, where pacing device 902 and/or LCP 904 may send signals to othersensors/devices 910, and other sensors/devices 910 relay the receivedsignals to external device 906. However, this is just one contemplatedexample.

In some cases, the various devices of system 900 may communicate viapathway 908 using conducted communication signals. Accordingly, devicesof system 900 may have components that allow for such conductedcommunication. For instance, the devices of system 900 may be configuredto transmit conducted communication signals (e.g. current and/or voltagepulses) into the patient's body via one or more electrodes of atransmitting device, and may receive the conducted communication signals(e.g. pulses) via one or more electrodes of a receiving device. Thepatient's body may “conduct” the conducted communication signals (e.g.pulses) from the one or more electrodes of the transmitting device tothe electrodes of the receiving device in the system 900. In suchembodiments, the delivered conducted communication signals (e.g. pulses)may differ from pacing pulses, defibrillation and/or cardioversionpulses, or other electrical stimulation therapy signals. For example,the devices of system 900 may deliver electrical communication pulses atan amplitude/pulse width that is sub-threshold (e.g. does not capturethe heart, phrenic nerve, and/or other tissue). Although, in some cases,the amplitude/pulse width of the delivered electrical communicationpulses may be above a capture threshold, but may be delivered during anirrelevant time period. For example, the amplitude/pulse width of thedelivered electrical communication pulses may be above a capturethreshold of the heart, but may be delivered during a refractory periodof the heart and/or may be incorporated in or modulated onto a pacingpulse, as desired.

Delivered electrical communication pulses may be modulated in anysuitable manner to encode communicated information. In some cases, thecommunication pulses may be pulse width modulated and/or amplitudemodulated. Alternatively, or in addition, the time between pulses may bemodulated to encode desired information. In some cases, conductedcommunication pulses may be voltage pulses, current pulses, biphasicvoltage pulses, biphasic current pulses, or any other suitableelectrical pulse as desired.

In the example of FIG. 1, system 20 may be communicatively coupled inany number of ways in different embodiments. For instance, in someembodiments, ICD 600 may be the only device which delivers electricalcommunication pulses, while pacing device 500 and/or LCP 550 may only beconfigured to receive electrical communication pulses. In otherembodiments, all devices of system 20 may be configured to deliverelectrical communication pulses and/or receive electrical communicationpulses. In embodiments where pacing device 500 is configured to deliverelectrical communication pulses, pacing device 500 may be configured todeliver electrical communication pulses via one or more differentcombinations of electrodes 507 a-507 d, 505 a-505 e, and/or 510 a-510 e.For instance, when delivering an electrical communication pulse, pacingdevice 500 may deliver electrical communication pulses via a first setof electrodes. The first set of electrodes may be any pair of electrodesfrom between electrodes 507 a-507 d, 505 a-505 e, and 510 a-510 e. Asone example, pacing device 500 may deliver communication pulses via afirst set of electrodes that includes electrodes 505 a and 505 e, orelectrodes 505 b and 507 a, or some other combination. In some cases,the particular set of electrodes that is used may change over time.Although, in other embodiments, the first set of electrodes may compriseany combination of any number of electrodes from electrodes 507 a-507 d,505 a-505 e, and 510 a-510 e.

In some instances, pacing device 500 may use a different set ofelectrodes by which to deliver electrical communication pulses dependingfor which device the electrical communication pulses are intended. Forexample, pacing device 500 may deliver electrical communication pulsesvia one particular set of electrodes if the electrical communicationpulses are intended for LCP 550. However, if the electricalcommunication pulses are intended for ICD 600, pacing device may deliverthe electrical communication pulses via another set of electrodes thatis a different combination of electrodes than the electrodes pacingdevice 500 uses to deliver electrical communication pulses intended forLCP 550. Although, in some instances, pacing device 500 may use the sameset of electrodes when delivering electrical communication pulsesintended for any device.

Additionally, pacing device 500 may use still another, different set ofelectrodes when receiving communication signals. The receiving set ofelectrodes may be different from the communicating set of electrodes,but this is not required.

LCP 550 and ICD 600 may deliver electrical communication pulses andreceive communication signals in a similar manner as pacing device 500.For example, LCP 550 and ICD 600 may use a desired combination of theirelectrodes to deliver electrical communication pulses and/or to receivecommunication signals. Additionally, LCP 550 and/or ICD 600 may, in someembodiments, use different vectors when communicating with differentdevices. However, in some cases, LCP 550 and/or ICD 600 may use the samevector when communicating with different devices.

FIG. 5 is a schematic diagram of an illustrative pacing device 500. Theexample pacing device 500 includes body 502 having a proximal end 520and a distal end 522, sometimes with extensions 501 and/or 503. In somecases, extension 501 and/or extension 503 may not be included. In somecases, the extensions 501 and/or 503 may be integrally formed with thebody 502. In other cases, the extensions 501 and/or 503 and body 502 aremodular components, where one or more appropriate extensions 501 and/or503 may be selected by a physician for a particular application andconnected to the body 502. Body 502 may be a unitary housing in whichone or more components of pacing device 500 are housed. Body 502 maygenerally include a biocompatible material, such as a biocompatiblemetal or polymer, and, when implanted within a patient's body, mayhermetically seal the components of pacing device 500 from fluids andtissues of the patient's body. Pacing device 500 may additionally haveone or more electrodes, such as electrodes 507 a-507 d, which in theexample shown, reside on body 502. It is contemplated in some cases thatbody 502 may have a different number of electrodes, or no electrodes atall.

In some instances body 502 may include a docking hub 504 extending fromproximal end 520. In some cases, docking hub 504 may have an extension531 projecting from body 502 connected to an appendage 533. In theexample shown in FIG. 5, appendage 533 may have a greater diameter thanextension 531. During implantation, a positioning device may releasablycouple to docking hub 504. When coupled, movement of the positioningdevice may translate to body 502, thereby allowing a user to positionpacing device 500 during implantation. In some cases, instead ofextension 531 and appendage 533, docking hub 504 may include one-half ofan interlocking mechanism, and the positioning device may have thesecond half of the interlocking mechanism, which may releasably coupleto the interlocking mechanism of docking hub 504.

In some instances, body 502 may include a fixation mechanism 535.Fixation mechanism 535 may be configured to maintain pacing device 100within coronary sinus 11 when pacing device 500 is implanted within thecoronary sinus of the heart 10. In at least some additional embodiments,fixation mechanism 535 may further maintain body 502 in a desireddisposition with respect to the lumen of coronary sinus 11, for instancefloating in the middle of the lumen or pressed up against the wall ofcoronary sinus 11. For instance, fixation mechanism 535 may include oneor more tines or talons that may embed within the wall of coronary sinus11 when pacing device 500 is implanted. In other instances, body 502 maynot include fixation mechanism 535. In such embodiments, pacing device502 may be held within coronary sinus 11 between extension 501 and 503,each of which may be secured in place. In embodiments where pacingdevice 100 does not include extension 501, pacing device 500 may includea fixation mechanism extending from distal end 522. For instance, pacingdevice 500 may include one or more fixation elements similar to fixationelements 506 or 512. In other embodiments, pacing device 500 may includea coiled extension, where the coiled extension has a greater diameterthan the diameter of coronary sinus 11. The friction between the coiledextension and the walls of coronary sinus 11 may help hold pacing device500 in place within the coronary sinus 11.

In at least some embodiments, body 502 may have guide wire port 541. Insome cases, guide wire port 541 may be disposed proximate distal end 522of body 502 and may be configured to receive a guide wire. Where pacingdevice 500 includes extension 501, extension 501 may include acorresponding guide wire port 543 located proximate distal end 526 ofextension 501. In such embodiments, a guide wire may be placed down thegreat cardiac vein 13. The pacing device 500 may be tracked over theguide wire by threading extension 501 over the proximal end of the guidewire, and then advancing the pacing device 500 over the guide wire untilin position. In embodiments where pacing device 500 does not includeextension 501, body 502 may include a second guide wire port.

In some cases, body 502 may include extension 503 extending fromproximal end 520 of the body 502. Generally, extension 503 may be a thinand flexible member, particularly in relation to body 502. For instance,extension 503 may be between two and ten times the length of body 502.Extension 503 may contain one or more electrical conductors thatelectrically connect electrodes 505 a-505 e residing on extension 503with one or more components within body 502. In some embodiments,electrodes 505 a-505 e may be disposed proximate distal end 524 ofextension 503. However, in other embodiments, electrodes 505 a-505 e maybe disposed along the length of extension 503. In some instances, distalend 524 of extension 503 may terminate in an electrode, such aselectrode 505 a. Extension 503 may have a different number ofelectrodes, or no electrodes at all. Accordingly, in this manner,electrodes 505 a-505 e may be spaced apart from body 502. In some cases,one or more of the electrodes 505 a-505 e are spaced apart from a body502 that is located in the coronary sinus 11 by a sufficient distance toelectrically engage the septum 15 of the right atrium 21.

In some embodiments, extension 503 may be biased to form a shape thatdirects the distal end 524 toward the septum 15 of the right atrium 21.Distal end 524 of extension 503 may sometimes include one or morefixation elements 506. When pacing device 500 is implanted, fixationelements 506 may help secure the distal end 524 of extension 503 inright atrium 21 proximate septum 15, or, in some embodiments, to septum15. In some instances, extension 503 may include a docking hub 508 whichextends proximally from the distal end 524 of extension 503. In someinstances, docking hub 508 may be similar to docking hub 504. Forexample, docking hub 508 may include an extension and an appendage. Or,docking hub 508 may include one-half of an interlocking mechanism. In atleast some instances, docking hub 508 may releasably couple to the samepositioning device that may releasably couple to docking hub 504. Aswith docking hub 504, when docking hub 508 is releasably coupled to thepositioning device, movement of the positioning device may translate tothe distal end 524 of extension 503 thereby allowing a user to maneuverthe distal end 524 of extension 503 into position within heart 10.

As mentioned, in some instances, pacing device 500 may optionallyinclude extension 501 extending from distal end 522 of body 502.Extension 501 may be similar to extension 503 in that extension 501 maybe a thin and flexible member, particular in relation to body 502. Forinstance, extension 503 may be between two and ten times the length ofbody 502. Additionally, similarly to extension 503, extension 501 mayhave one or more fixation elements 512. In some cases, fixation elements512 may be disposed at or near the distal end 526 of extension 501. Insome cases, extension 501 may include one or more electrodes 510 a-510e. As with electrodes 505 a-505 e, electrodes 510 a-510 e may bedisposed proximate distal end 524 of extension 501, or may be spread outalong the length of extension 501. In some embodiments, extension 501may terminate at distal end 524 in an electrode. In some cases, one ormore of the electrodes 510 a-510 e are spaced apart from a body 502 thatis located in the coronary sinus 11 by a sufficient distance toelectrically engage the left ventricle 27. In some instances, extension501 may have one or more electrodes that are placed to align with theleft atrium 23 to allow the pacing device 500 to sense and/or pace theleft atrium 23 of the patient's heart. In some cases, extension 501 maybe biased to form a shape such as a helical coil or one or more loops.

FIG. 6 is a schematic block diagram of one or more electronics modulesthat may be contained within body 502 of pacing device 500. In someinstances, pacing device 500 may include energy storage module 532,processing module 534, communication module 536, pulse generator module538, electrical sensing module 542, and/or mechanical sensing module544. FIG. 6 also depicts conductors 546, 548 that may extend from one ormore of modules 532, 534, 536, 538, 542, and/or 544 through extensions503 and/or 501. Accordingly, in at least some embodiments, all of theelectronic elements and energy storage modules of pacing device 500 maybe contained within body 502, while only one or more conductors extendthrough extension 503 and/or extension 501 where included. Where pacingdevice 500 includes any of modules 532, 534, 536, 538, 542, and/or 544,the modules 532, 534, 536, 538, 542, and/or 544 may be similar to themodules of the same name described with respect to LCP 550 in FIG. 2.

FIG. 7 depicts an alternative embodiment of pacing device 500, andincludes one or more features that may be additionally or alternativelycombined, in other embodiments, with some or all of the featuresdescribed with respect the pacing device 500 described in FIG. 6.Accordingly, in some instances, as depicted in FIG. 7, body 502 ofpacing device 500 may be split into a rigid first portion 502 a and arigid second portion 502 b. In some cases, rigid first portion 502 a maypartially, or wholly, house the electronics of pacing device 500, asdepicted in FIG. 7 and may be represented by electronics module 545.Additionally, rigid second portion 502 b may partially, or wholly, housethe energy storage module of pacing device 500, as depicted in FIG. 7and may be represented by energy storage module 547. However, in othercases, rigid first portion 502 a may partially, or wholly, house theenergy storage module, and rigid second portion 502 b may partially, orwholly, house the electronics of pacing device 500. In some instances,rigid first portion 502 a and rigid second portion 502 b may beconnected by a flexible connector 511. Flexible connector 511 may allowrigid first portion 502 a and rigid second portion 502 b to move and/orrotate with respect to each other, allowing each portion to be disposedat an angle relative to the other portion when implanted. Electronicsmodule 545 and energy storage module 547 may be connected by one or moreflexible electrical conductors 537 in the flexible connector 511.Although depicted in FIG. 7 as only including rigid first portion 502 aand rigid second portion 502 b, it is contemplated that body 502 ofpacing device 500 may be split into any number of rigid portionsconnected by flexible connectors.

In some instances, pacing device 500 may include an eccentric biaselement 549. Eccentric bias element 549 may be configured to bias theposition of pacing device 500, when implanted, toward one side ofcoronary sinus 11. For instance, eccentric bias element 549 may becurved piece of biocompatible metal or polymer that extends away frombody 502. When implanted, eccentric bias element 549 may press against awall of coronary sinus 11 and impart an opposing force on body 502. Thisopposing force may act to push body 502 toward an opposite wall ofcoronary sinus 11, and bias the disposition of body 502 within coronarysinus 11. Biasing body 502 toward a side of coronary sinus 11 may helpimprove blood flow through coronary sinus 11 when pacing device 500 isimplanted relative to blood flow through coronary sinus 11 when body 502does not include eccentric bias element 549. In some embodiments,eccentric bias element 549 may include one or more fixation elementsdisposed proximate the end of eccentric bias element 549 that extendsaway from body 502. In such embodiments, eccentric bias element 549 maybe configured to both bias the position of body 502 toward a side ofcoronary sinus 11 and secure the location of body 502 of pacing device500 within coronary sinus 11. In such embodiments, body 502 may notinclude fixation element 535.

FIG. 8 depicts an example where extension 501 may additionally oralternatively be biased to form a helical coil shape. When so provided,extension 501 may not include one or more fixation elements 512 disposedproximate distal end 526 of extension 501. Instead, extension 501 may bebiased to form a helical coil shape that exerts an outward force on thegreat cardiac vein 13. When assuming the helical coil shape, the helicalcoil may have a diameter that is larger than the diameter of coronarysinus 11 and/or great cardiac vein 13. In such embodiments, whenimplanted, the friction between the helical coil shape of the extension501 and the wall of coronary sinus 11 and/or great cardiac vein 13 mayhold extension 501 in place within coronary sinus 11 and/or greatcardiac vein 13. Even so, it is contemplated that in some casesextension 501 may include one or more fixation elements 512 in additionto being biased to form helical coil shape. Additionally, in embodimentswhere pacing device 500 does not include extension 501, pacing device500 may include a fixation extension extending from distal end 522 ofbody 502. In such embodiments, the fixation extension may be biased toform a helical coil shape similar to extension 501 of FIG. 8. In somecases, the fixation extension may be shorter than extension 501 and maynot include electrodes.

FIGS. 9A-9C depict illustrative embodiments of distal end 524 ofextension 503. In the embodiment of FIG. 9A, extension 503 may be a longand flexible member, particularly in relation to body 502. For instance,extension 503 may be between two and ten times the length of body 502.In the embodiment of FIG. 9A, distal end 524 of extension 503 maymaintain the same form as the rest of extension 503. In suchembodiments, fixation elements 506 and docking hub 504 may extenddirectly from extension 503.

In the illustrative embodiment of FIG. 9B, extension 503 may again be along and flexible member, particularly in relation to body 502. Forinstance, extension 503 may be between two and ten times the length ofbody 502. However, in the embodiment of FIG. 9B, extension 503 mayterminate in a head 528. Head 528 may generally have a diameter greaterthan the diameter of the rest of extension 503 and may have a proximalend 529 b and a distal end 529 a. In the embodiment of FIG. 9B,extension 503 may connect directly to proximal end 529 b of head 528.Docking hub 508 may also connect directly to proximal end 529 b of head528. As depicted in FIG. 9B, in at least some embodiments, fixationelements 506 may be disposed on head 528, and at least one of electrodes505 a-505 e may also be disposed on head 528. In some cases, extension503 may only include two electrodes, one to act as a cathode and one toact as an anode when pacing device 500 delivers electrical stimulationtherapy to right atrium 21, and both electrodes may be disposed on head528. In some cases, one of the electrodes may be on the distal tip 529 aof the head 528.

FIG. 9C depicts another embodiment of extension 503. In the embodimentof FIG. 9C, extension 503 may be a long and flexible member,particularly in relation to body 502. For instance, extension 503 may bebetween two and ten times the length of body 502. As with the embodimentof FIG. 9B, in the embodiment of FIG. 9C, extension 503 may terminate inhead 528. Head 528 may generally have a diameter greater than thediameter of the rest of extension 503 and may have a proximal end 529 band a distal end 529 a. In the illustrative embodiment of FIG. 9C,extension 503 may connect to a side of head 528, while docking hub 508may connect directly to proximal end 529 b of head 528. As depicted inFIG. 9C, in at least some embodiments, fixation elements 506 may bedisposed on head 528, and at least one of electrodes 505 a-505 e mayalso be disposed on head 528. In some cases, extension 503 may onlyinclude two electrodes, one to act as a cathode and one to act as ananode when pacing device 500 delivers electrical stimulation therapy toright atrium 21, and both electrodes may be disposed on head 528. Insome cases, one of the electrodes may be on the distal tip 529 a of thehead 528.

FIG. 9D depicts another embodiment of extension 503. In the embodimentof FIG. 9D, extension 503 may be a long and flexible member,particularly in relation to body 502. For instance, extension 503 may bebetween two and ten times the length of body 502. Extension 503 mayterminate in head 528. In the embodiment of FIG. 9D, head 528 maygenerally be round or spherical in shape. Additionally, head 528 mayhave a diameter greater than the diameter of the rest of extension 503and may have a proximal end 529 b and a distal end 529 a. Extension 503may additionally have collar 530 connected to distal end 529 a of head528 and disposed between fixation elements 506 and head 528. As depictedin FIG. 9D, extension 503 may not have hub 508. In these cases, head 528may directly be a part a coupling system for maneuvering distal end 524to a desired location. Although shown with five electrodes 505 a-e, insome cases, extension 503 may only include two electrodes, one to act asa cathode and one to act as an anode when pacing device 500 deliverselectrical stimulation therapy to right atrium 21, and both electrodesmay be disposed on head 528. In some cases, one of the electrodes may beon the distal tip 529 a of the head 528.

FIGS. 10A and 10B are plan views of distal ends 524 of extension 503where extension 503 includes alternative fixation elements. In theembodiment of FIG. 10A, instead of fixation elements 506 including oneor more tines, fixation element 506 includes a helical wire coil orscrew type member. In such embodiments, the helical wire coil may bescrewed into septum 15 to secure the distal end 524 of extension 503within right atrium 21.

In the embodiment of FIG. 10B, fixation elements 506 are depicted astalons. In such embodiments, the talons may be biased to have apredetermined shape. For example, when the talons are free to assumetheir predetermined shape, the talons may extend from distal end 524 ofextension 503 and curl backwards away from the distal end 524 ofextension 503. When implanted, the talons may be forced into a straightconfiguration by a delivery catheter or the like, and may be pushed intoand puncture septum 15 before curling back into the right atrium,thereby securing the distal end 524 of extension 503 within right atrium21.

Although the alternative fixation elements of FIGS. 10A and 10B weredescribed with respect to extension 503, in some instances, the one ormore fixation elements 512 and/or fixation mechanism 535 may also takeany of the forms described with respect to FIGS. 10A and 10B. Further,in various embodiments, the specific fixation elements of extension 501,extension 503, and fixation mechanism 535 on body 502 may differ fromeach other, as desired.

FIG. 11 depicts a close-up of plan view pacing of device 500 implantedwithin heart 10 of FIG. 1. In FIG. 11, pacing device 500 includes rigidfirst portion 502 a and rigid second portion 502 b. Pacing device 500may be configured such that rigid first portion 502 a is at leastpartially disposed within coronary sinus 11 as shown. In some instances,rigid first portion 502 a may be completely disposed within coronarysinus 11. For instance, rigid first portion 502 a may have a sizesufficient to fit within coronary sinus 11 while still allowing bloodflow through coronary sinus 11. As described with respect to FIG. 7,rigid first portion 502 a may house some or all of the electronics ofpacing device 500. Accordingly, when rigid first portion 502 a isdisposed completely within coronary sinus 11, all of the electronics ofpacing device 500 may be disposed within coronary sinus 11.

Additionally, as depicted in FIG. 11, pacing device 500 may beconfigured such that rigid second portion 502 b is at least partiallydisposed within right atrium 21 of heart 10. For instance, rigid secondportion 502 b may have dimensions smaller than that of right atrium 21to allow rigid second portion 502 b to fit within right atrium 21. Insome embodiments, rigid second portion 502 b may be completely disposedwithin right atrium 21 of heart 10. As described with respect to FIG. 7,rigid second portion 502 b may house some or all of the energy storagemodule of pacing device 500. Accordingly, when rigid second portion 502b is disposed completely within right atrium 21 of heart 10, the entireenergy storage module of pacing device 500 may be disposed within rightatrium 21. In other embodiments, the energy storage module may be placedin the rigid first portion 502 a, and the rigid second portion 502 b mayhouse the electronics and be very light with less mass relative to rigidfirst portion 502 a. These are just some examples of how the electronicsand energy storage module may be split between rigid first portion 502 aand rigid second portion 502 b. In some cases, flexible connector 511may extend through coronary sinus ostium 12 to connect rigid firstportion 502 a to rigid second portion 502 b.

In the embodiment of FIG. 11, where only a portion of body 502 of pacingdevice 500 is disposed within coronary sinus 11, coronary sinus 11 mayexperience increased blood flow relative to embodiments where a greaterportion, or all of, body 502 of pacing device 500 is disposed withincoronary sinus 11. This is because the body 502 will present less of anocclusion to the coronary sinus 11. Additionally, where docking hub 504is disposed on rigid second portion 502 b and disposed within rightatrium 21, docking hub 504 may be easier to access than if disposed inother locations, thereby allowing for easier retrieval of pacing device500, should pacing device 500 need to be removed. Further, as at least aportion of body 502 of pacing device 500 resides within coronary sinus11, pacing device 500 may place less stress on septum 15 of heart 10where extension 503 attaches to septum 15. For instance, at least aportion of the mass of pacing device 500 may be supported by coronarysinus 11 as opposed to the entire mass of pacing device 500 hanging offof septum 15 by virtue of connection between extension 503 and septum15, for example in embodiments where no weight of pacing device 500 issupported by coronary sinus 11. The septum 15 is often thin andpotentially susceptible to damage if too large of a mechanical load isapplied.

FIG. 12 depicts another close-up of pacing device 500 implanted withinheart 10 of FIG. 1. In FIG. 12, body 502 of pacing device 500 may be aunitary housing, and pacing device may be configured such that themajority of body 502 is disposed within coronary sinus 11. In somecases, body 502 may have docking hub 504 extending from body 502, andpacing device 500 may be configured such that when pacing device 500 isimplanted, docking hub 504 extends through coronary sinus ostium 12 andinto the right atrium 21. Additionally, and in the embodiment shown, theextension 503 may be configured to extend through coronary sinus ostium12 and over to the septum 15 of the right atrium 21.

In the embodiment of FIG. 12, where docking hub 504 extends throughcoronary sinus ostium 12, docking hub 504 may be easier to access thanif disposed in other locations, thereby allowing for easier retrieval ofpacing device 500, should pacing device 500 need to be removed. In theembodiment of FIG. 12, a majority of body 502 of pacing device 500resides within coronary sinus 11. This may place less stress on septum15 of heart 10 where extension 503 attaches to septum 15 because amajority of the mass of pacing device 500 may be supported by coronarysinus 11 as opposed to being supported by septum 15.

FIGS. 13A-13C are example cross-sections of body 502 of pacing device500 as viewed along line A-A in FIG. 11. In these embodiments, body 502of pacing device 500 may have a non-circular cross-section shape. Forinstance, as depicted in FIG. 13A, body 502 may have a circularsegmented shape, with one rounded side and one flat side. In theseembodiments, the circular segmented shape may generally conform to theshape of coronary sinus 11. Such a shape may allow for a greater and/orsmoother flow of blood past body 502 within coronary sinus 11. FIG. 13Bdepicts another embodiment of body 502 that has a toroidalcross-sectional shape. FIG. 13C depicts another embodiment of body 502that has a generally flat rectangular cross-section. In still otherinstances, body 502 may have a circular cross-section. Each of thesecross-sectional shapes may have advantages for decreasing the amount ofcross-sectional area of coronary sinus 11 that body 502 takes up, andmay decrease the amount of turbulence that body 502 imparts to bloodflowing past body 502. It is contemplated that the body 502 need nothave the same cross sectional shape along its entire length. Also, inthose instances where body 502 comprises a rigid first portion 502 a anda rigid second portion 502 b, each of rigid first portion 502 a andrigid second portion 502 b may have the same or different cross-sectionshapes.

Additionally, body 502 may have a cross-section diameter or areasufficient to fit within coronary sinus 11. Sizes of coronary sinus 11may vary in humans between about 0.12 inches (3 mm) to about 0.6 inches(15 mm). Diameter of body 502 may range, in different embodiments,between about 0.1 inches (2.54 mm) to about 0.4 inches (10 mm). Thesesizes may allow body 502 to be implanted within different sized coronarysinuses while still allowing for sufficient blood flow through coronarysinus 11.

In some embodiments, pacing device 500 may be delivered to the implantsite with a guide catheter, such as guide catheter 1000 of FIG. 14A.Guide catheter 1000 may generally be sized to be able to receive pacingdevice 500, a guide wire 1002, and positioning device 1004 within alumen of the guide catheter 1000. When disposed within guide catheter1000, pacing device 500 may be connected to positioning device 1004 byinterlocking mechanism 1006. Interlocking mechanism 1006 may releasablycouple with docking hub 504 of body 502.

To deliver pacing device 500 to the implant site, pacing device 500 maybe threaded over guide wire 1002, which may have already been positionedwithin coronary sinus 11 or down the great cardiac vein 13. In somecases, guide wire 1002 may be threaded through guide wire port 433 andout guide wire port 431, as depicted in FIG. 14A. Guide catheter 1000,including pacing device 500, may then be advanced over the guide wire1002. Once in position, such as in the coronary sinus 11 of the heart,the guide catheter 1000 may be retracted, for example in the directionof arrows 1010, thereby exposing pacing device 500, as depicted in FIG.14B. The pacing device 500 may be kept in position by positioning device1004. In other embodiments, instead of retracting guide catheter 1000,positioning device 1004 may be used to push pacing device 500 out theend of guide catheter 1000.

In some embodiments, positioning device 1004 may be semi-flexible, butretain sufficient rigidity to impart force to pacing device 500 whenmaneuvered. For instance, once guide catheter 1000 is in position, andguide catheter 1000 is then retracted, a user may manipulate positioningdevice 1004 to impart force on pacing device 500 through docking hub504. In this manner, the user may maneuver pacing device 500 to adesired location. Once in position, the user may decouple interlockingmechanism 1006 from docking hub 504, and may retract guide wire 1002 andguide catheter 1000, including positioning device 1004. In otherembodiments, after decoupling positioning device 1004 from docking hub504, the user may maneuver positioning device 1004 and coupleinterlocking mechanism 1006 to docking hub 508 of the extension 503. Theuser may then maneuver distal end 524 of extension 503 to a desiredlocation (e.g. to the septum of the right atrium) before decouplingpositioning device 1004 from docking hub 508. Once decoupled, the usermay then retract guide catheter 1000 from the body, includingpositioning device 1004.

In some instances, instead of decoupling interlocking mechanism 1006 andpositioning device 1004 from docking hub 504 and coupling interlockingmechanism 1006 and positioning device 1004 to docking hub 508, guidecatheter 1000 may include two separate positioning devices 1004, 1012,such as depicted in FIG. 15. Positioning device 1012 may additionallycomprise interlocking mechanism 1014 for coupling to docking hub 508.This may allow a user to maneuver body 502 into place using positioningdevice 1004 and to maneuver distal end 524 of extension 503 into placeusing positioning device 1012. In still other instances, a singlepositioning device, such as positioning device 1004, may includemultiple interlocking mechanisms. For example, a first interlockingmechanism may interlock with docking hub 504, which a secondinterlocking mechanism may interlock with docking hub 508. A user maythen use positioning device 1004 to position both pacing device 1004 anddistal end 524 of extension 503.

FIGS. 16A and 16B illustrate an illustrative positioning device 1004 andinterlocking mechanism 1006. In the example shown in FIGS. 16A and 16B,positioning device 1004 may include a sheath 1051. In some instances,sheath 1051 may include one or more structural features that impart asufficient level of rigidity to allow a user to push, pull, andotherwise move positioning device 1004 and body 502 or distal end 524 ofextension 503 when positioning device is coupled to either body 502 ordistal end 524 of extension 503. For instance, in some embodiments,sheath 1051 may be a braided sheath, or have a braided covering or innersupport member coupled to sheath 1051. In other embodiments, positioningdevice 1004 may include a coiled wire coupled to sheath 1051.

In the example shown, interlocking mechanism 1006 may include members1053 which terminate at one end in prongs 1055. In some cases, members1053 may extend all the way down sheath 1051 and may be manipulated by auser to transition prongs 1055 between an open position (see FIG. 16A)and a closed position (see FIG. 16B). FIG. 16A depicts prongs 1055 in anopen configuration and disposed proximate docking hub 504.

When coupling interlocking device 1006, a user may position prongs 1055in a position close-to or around docking hub 504. Once in position, theuser may manipulate members 1053 to transition prongs 1055 from the openposition into the closed position. FIG. 16B depicts prongs 1055 in theclosed position around docking hub 508.

In the example shown in FIGS. 16A and 16B, sheath 1051 may be able to bemoved relative to members 1053. For example, in the open position,sheath 1051 may not be disposed around prongs 1055 as shown in FIG. 16A.Prongs 1055 may be biased such that when prongs 1055 are outside of thesheath 1051, prongs 1055 may expand to a greater extent than thediameter of sheath 1051. To transition prongs 1055 to the closedposition, a user may simply slide sheath 1051 relative to members 1053,such as toward prongs 1055. As sheath 1051 is slid toward prongs 1055,at least a portion of prongs 1055 may be compressed by sheath 1051. Thiscompression of prongs 1055 may cause prongs 1055 to transition to theclosed position, as depicted in FIG. 16B.

FIGS. 17A-17C depict another embodiment of positioning device 1004 andinterlocking mechanism 1006. FIG. 17A depicts positioning device 1004and interlocking mechanism 1006 disposed proximate a docking hub 504. Inthese embodiments, positioning device 1004 may include a sheath 1051, asdescribed with respect to FIGS. 16A-16B. Interlocking mechanism 1006 mayinclude inflation member 1061 and balloon 1063. In some cases, balloon1063 may have a generally toroidal shape, or any other suitable shapewith a hole or recess. To couple to docking hub 504, a user may positionballoon 1063 in an un-inflated state around docking hub 504, as shown inFIG. 17B. Once balloon 1063 is positioned around docking hub 504, a usermay inflate balloon 1063 by injecting inflation media through inflationmember 1061 and into balloon 1063. When balloon 1063 inflates, itexpands around docking hub 504, thereby securing docking hub 504 toballoon 1063 and thus to positioning device 1004, as depicted in FIG.17C. When coupled, a user may maneuver positioning device 1004, andconsequently body 502 attached to docking hub 504, into a desiredposition.

FIGS. 18A-18D depict additional embodiments of positioning device 1004and interlocking mechanism 1006. FIG. 18A depicts positioning device1004 and extension 503 disposed within guide catheter 1000. In theexample of FIG. 18A, head 528 may be generally round or spherical, butin other cases head 528 may take other shapes. In these examples, head528, and extension 503 more generally, may not include a hub. Instead,coupling of positioning device 1004 to extension 503 may be accomplishedby a coupling directly with head 528. As depicted in FIG. 18A,positioning device 1004 may be a generally hollow tube with interlockingmechanism 1006 disposed at one end. Interlocking mechanism 1006 maygenerally comprise arms 1011 and cut-out 1015. Cut-out 1015, as depictedin FIG. 18A, may comprise a slot extending away from the end ofpositioning device 1004 and a round cut-out disposed proximate the endof positioning device 1004. Arms 1011 extend beyond the round cut-outtoward the end of interlocking mechanism 1006. The round cut-out and thearms may be sized to engage with head 528, as seen in FIG. 18A. Forinstance, the round cut-out may be slightly smaller than head 528 suchthat arms 1011 bend around head 528 and firmly secure 528 to positioningdevice 1004. Arms 1011 may be made from a material or designed in such away that arms 1011 are able to flex due to external forces, for examplewhen head 528 is inserted in the round cut-out, but rigid enough toreturn to an unstressed state when the external force is removed.

Once guide catheter has been maneuvered into a desired position, the endof positioning device 1004 including interlocking mechanism 1006 whichis coupled to head 528, may be pushed out of guide catheter 1000, orguide catheter 1000 may be retraced relative to positioning device 1004and extension 503. FIG. 18B shows the portion of positioning device 1004including interlocking mechanism 1006, and coupled to extension 503,outside of guide catheter 1000. When head 528 is coupled to interlockingmechanism 1006, extension 503 may be free to rotate about head 528 ashead 528 is able to rotate within the round cut-out. However, whileinterlocking mechanism 1006 and extension 503 are disposed within guidecatheter 1000, the walls of guide catheter 1000 may constrain suchrotation. Once outside of guide catheter 1000, extension 503 may rotateabout interlocking mechanism 1006, as seen in FIG. 18C, which shows aside view of positioning device 1004 coupled to head 528. Where cut-out1015 includes a slot, the slot may allow for a greater range of rotationof head 528 and extension 503 by allowing collar 530 and/or otherportions of extension 503 to rotate into the slot. The rotation of head528 when coupled to interlocking mechanism 1006 may be important forproperly orienting head 528 with respect to the desired implant site.For instance, a user may manipulate positioning device 1004 to positionpositioning device 1004, and more specifically the end of positioningdevice 1004 including interlocking mechanism 1006, at a desired implantlocation. Once positioning device 1004 is in place, implanting head 528may involve decoupling head 528 from interlocking mechanism 1006.However, once head 528 is decoupled, the user may no longer have anycontrol over the positioning of head 528. Accordingly, allowing for head528 to rotate when coupled to interlocking mechanism 1006 may assist inproperly orienting extension 503 for implantation. In some embodiments,extension 503 may have a coiled or otherwise bent shape. Once extension503 is free from the constraints of guide catheter 1000, extension 503may twist into its coiled or otherwise bent shape. As extension 503attempts to take on its coiled or otherwise bent shape, extension 503may rotate about interlocking mechanism 1006 and orient extension 503 ina desired orientation, as seen in FIG. 18C.

Once positioning device 1004 is positioned at the implant location, astylet or other pushing member 1018 may be inserted into the lumen ofpositioning device 1004. Stylet 1018 may be advanced toward interlockingmechanism 1006 and head 528. As stylet 1018 contacts head 528, stylet1018 applies pushing forces head 528 to decouple head 528 frominterlocking mechanism 1006, for example by pushing head 528 out of arms1011 and cut-out 1015. Positioning device 1004 may then be retracted ashead 528 is held in place by fixation member 506. It should beunderstood that although the embodiments of FIGS. 18A-18D are describedwith respect to positioning device 1004 and extension 503, a similarinterlocking mechanism may be used in conjunction with body 502.

FIGS. 19-24 depict the use of a guide wire and guide catheter 1000 inthe implantation of pacing device 500 within heart 10. In someembodiments, implanting pacing device 500 within heart 10 may begin bypositioning a guide wire within heart 10, such as guide wire 1201. Insome instances, guide wire 1021 may have one or more radiopaque markersdisposed on an end of guide wire 1201. Such radiopaque markers may allowfor easier viewing of guidewire 1201 through one or more medical imagingsystems as the guide wire 1201 is maneuvered into position with theheart 10. In some embodiments, the radiopaque markers may be spacedapart from each other by a known distance. In such embodiments, bycounting the number of radiopaque markers between two features withinheart 10, a distance may be determined between the two features. In someembodiments, pacing device 500 may be manufactured in a variety ofsizes, or various portions of pacing device 500, such as body 502 andextension 503, may be manufactured in various sizes and lengths. Bydetermining a distance between different features of the patient's heart10, for instance between the coronary sinus ostium 12 and septum 15 inthe right atrium 21, as depicted in FIG. 19, an appropriate sized body502 or extension 503 may be selected for the particular patient.

After measuring distances between various features of heart 10, or inembodiments where such measurements are not needed, guide wire 1201 maythen be positioned within the coronary sinus 11, as depicted in FIG. 20.In some embodiments, guide wire 1201 may be maneuvered all the waythrough coronary sinus 11 and into great cardiac vein 13. Once guidewire 1201 is in place, guide catheter 1000, containing pacing device500, may be maneuvered over guide wire 1201 into place within heart 10.FIG. 21 depicts guide catheter 1000 and pacing device 500 positionedwithin coronary sinus 11.

Once pacing device 500 is in position, the guide catheter 1000 may beretracted. FIG. 22 depicts an example of how pacing device 500 may lookafter guide catheter 1000 has been retracted. In some embodiments, bodyportions 502 a and 502 b may be biased into a particular configurationsuch that when the guide catheter 1000 is retracted, body portions 502 aand 502 b assume the configuration shown in FIG. 22. In otherembodiments, body portions 502 a and 502 b may not be biased into aparticular configuration, and positioning device 1004 may be maneuveredto position body portion 502 b with respect to body portion 502 a asshown in FIG. 22. Once body portions 502 a and 502 b are in position,interlocking mechanism 1006 may be decoupled from docking hub 504, andthen coupled to docking hub 508. Positioning device 1004 may then bemaneuvered to position extension 503 into position, for example, withdistal end 524 disposed proximate septum 15, as depicted in FIG. 23. Inother embodiments, guide catheter 1000 may include a second positioningdevice that includes a second interlocking mechanism that is coupled todocking hub 508 during implantation of pacing device 500. In theseembodiments, instead of coupling interlocking mechanism 1006 to dockinghub 508, the second positioning device may be maneuvered to positionextension 503 into place. Once extension 503 has been positionedappropriately, guide catheter 1000, including positioning device 1004,and guide wire 1201 may be retracted all the way out of the patient,leaving pacing device 500 implanted within heart 10 as shown in FIG. 24.

Those skilled in the art will recognize that the present disclosure maybe manifested in a variety of forms other than the specific embodimentsdescribed and contemplated herein. For instance, as described herein,various embodiments include one or more modules described as performingvarious functions. However, other embodiments may include additionalmodules that split the described functions up over more modules thanthat described herein. Additionally, other embodiments may consolidatethe described functions into fewer modules.

Although various features may have been described with respect to lessthan all embodiments, this disclosure contemplates that those featuresmay be included on any embodiment. Further, although the embodimentsdescribed herein may have omitted some combinations of the variousdescribed features, this disclosure contemplates embodiments thatinclude any combination of each described feature. Accordingly,departure in form and detail may be made without departing from thescope and spirit of the present disclosure as described in the appendedclaims.

What is claimed is:
 1. An implantable medical device (IMD) comprising: abody having a proximal end and a distal end, wherein the body isconfigured to be disposed at least partially within the coronary sinusof a patient's heart; an extension having a length that extends distallyfrom the body, the extension is configured to traverse down the greatcardiac vein of the patient's heart and along at least part of the leftventricle, the extension being more flexible than the body; a firstelectrode supported by the extension and positioned at a longitudinallocation along the length of the extension so as to be adjacent the leftatrium of the patient's heart in order to sense one or more cardiacsignals of the left atrium of the patient's heart; a second electrodesupported by the extension and positioned distally of the firstelectrode and at a longitudinal location along the length of theextension so as to be adjacent the left ventricle of the patient's heartin order to deliver pacing pulses to the left ventricle of the patient'sheart; and a controller housed by the body and operatively coupled tothe first electrode and the second electrode, the controller configuredto detect a contraction of the left atrium based at least in part on oneor more cardiac signals sensed using the first electrode, and inresponse to detecting a contraction of the left atrium, deliver a pacingpulse to the left ventricle using the second electrode.
 2. The IMD ofclaim 1, wherein the extension comprises two or more second electrodeseach positioned at a different longitudinal location along the length ofthe extension so as to be adjacent a different part of the leftventricle of the patient's heart.
 3. The IMD of claim 2, wherein thecontroller is configured to deliver the pacing pulse to the leftventricle using less than all of the two or more second electrodes. 4.The IMD of claim 1, wherein the extension comprises two or more firstelectrodes each positioned at a different longitudinal location alongthe length of the extension so as to be adjacent a different part of theleft atrium of the patient's heart.
 5. The IMD of claim 4, wherein thecontroller is configured to detect a contraction of the left atriumbased at least in part on one or more cardiac signals sensed using lessthan all of the two or more first electrodes.
 6. The IMD of claim 4,wherein the controller is configured to deliver a pacing pulse to theleft atrium using less than all of the two or more first electrodes. 7.The IMD of claim 1, wherein the controller is configured to deliver apacing pulse to the left ventricle a predetermined time delay after thecontroller detects a contraction of the left atrium.
 8. The IMD of claim7, wherein the controller is configured to determine a heart rate of thepatient, and wherein the predetermined time delay is dependent on thedetermined heart rate of the patient.
 9. The IMD of claim 1, wherein theextension is pre-biased into a non-linear shape.
 10. The IMD of claim 1,wherein the extension comprises a fixation mechanism for securing theextension in the great cardiac vein.
 11. The IMD of claim 1, wherein thebody has a length, and wherein the length of the extension is between 2and 10 times longer than the length of the body.
 12. The IMD of claim 1,further comprising a communications module coupled to the controller,wherein the communications module is configured to support communicationwith one or more remote devices.
 13. The IMD of claim 1, wherein theextension and body are modular such that a physician can select aparticular extension from a set of different extensions and connect theselected extension to the body before implantation of the IMD.
 14. Animplantable medical device (IMD) comprising: a body having a proximalend and a distal end, wherein the body is configured to be disposed atleast partially within the coronary sinus of a patient's heart; anextension having a length that extends distally from the body, theextension is configured to traverse down the great cardiac vein of thepatient's heart and along at least part of the left ventricle, theextension being more flexible than the body; one or more firstelectrodes supported by the extension and each positioned at alongitudinal location along the length of the extension so as to beadjacent the left atrium of the patient's heart in order to sense one ormore cardiac signals of the left atrium of the patient's heart; two ormore second electrodes supported by the extension and positioneddistally of the first electrode and at spaced longitudinal locationsalong the length of the extension so as to be adjacent different partsof the left ventricle of the patient's heart in order to deliver pacingpulses to the left ventricle of the patient's heart; a controller housedby the body and operatively coupled to the first electrode and thesecond electrode, the controller configured to detect a contraction ofthe left atrium based at least in part on one or more cardiac signalssensed using one or more of the first electrodes, and in response todetecting a contraction of the left atrium, deliver a pacing pulse tothe left ventricle using one or more of the second electrodes apredetermined time delay after the controller detects the contraction ofthe left atrium; and the controller further configured to deliver apacing pulse to the left atrium using one or more of the firstelectrodes when needed.
 15. The IMD of claim 14, wherein the controlleris configured to deliver the pacing pulse to the left ventricle usingless than all of the two or more second electrodes.
 16. The IMD of claim14, wherein the extension is pre-biased into a non-linear shape.
 17. TheIMD of claim 14, wherein the extension comprises a fixation mechanismfor securing the extension in the great cardiac vein.
 18. An implantablemedical device (IMD) comprising: a body having a proximal end and adistal end, wherein the body is configured to be disposed at leastpartially within the coronary sinus of a patient's heart; an extensionhaving a length that extends distally from the body to a distal end, theextension is configured to traverse down the great cardiac vein of thepatient's heart and along at least part of the left ventricle, theextension being more flexible than the body; one or more electrodessupported by the extension; a controller housed by the body andoperatively coupled to the one or more electrodes; a power source housedby the body for providing power to the controller; a guide wire entranceport distal of the proximal end of the body; and a guide wire exit portdistal of the guide wire entrance port, wherein the IMD defines a guidewire lumen extending between the guide wire entrance port and the guidewire exit port.
 19. The IMD of claim 18, wherein the guide wire entranceport is proximate the distal end of the body or proximate a proximal endof the extension.
 20. The IMD of claim 18, wherein the guide wire exitport is proximate the distal end of the extension.